Probing new physics in semileptonic Λb decays

Abstract

In recent times, several hints of lepton nonuniversality have been observed in semileptonic B meson decays, both in the charged-current (b → clν l ) and neutral-current (b → sll) transitions. Motivated by these intriguing results, we perform a model-independent analysis of the semileptonic Λ b decays involving the quark level transitions b → ðu; cÞlν l , in order to scrutinize the nature of new physics. We constrain the new parameter space by using the measured branching ratios of the B þ c;u → τ þ ν τ , B → πτν τ processes and the existing experimental results on the R D ðÃÞ , R J=ψ , and R l π parameters. Using the constrained parameters, we estimate the branching ratios, forward-backward asymmetries, and hadron and lepton polarization asymmetries of the Λ b → ðΛ c ; pÞlν l processes. Moreover, we also examine whether there could be any lepton universality violation in these decay modes.

Model independent analysis of $$ B^* \rightarrow P \ell {\bar{\nu }}_\ell $$ decay processes

“…We use the theoretical expressions of these observables and their SM predictions from [32] and have listed them in Table 2. Br(B 0 → π + τ ν) < 2.5 × 10 −4 (9.40 ± 0.75) × 10 −5 Table. One can notice that, the Wilson coefficient corresponding to b → c scalar operators have χ 2 /d.o.f > 1, which implies that the fit is not robust.…”

Probing new physics in semileptonic $$\Xi _{b}\rightarrow \Lambda (\Xi _{c})\tau ^{-}\bar{\nu }_{\tau }$$ decays

“…was reported by [8] and deviated from the central value predicted in the SM 0.25-0.28 within 2σ range [11,12]. In addition, there is also discrepancy in the measured ratio [13]…”

“…We make the Wilson coefficients complex, though they are real in [23], and also we consider the constraints on the NP Wilson coefficients coming from R J/ψ and F D * L anomalies, which are not mentioned in [23]. In [13], the authors also consider the constraints on the complex NP Wilson coefficients, but they treat the b → u and b → c transitions separately. Therefore, the constraints on the NP Wilson coefficients are different from ours as is appropriate for both the b → u and the b → c transitions.…”

“…Therefore, the constraints on the NP Wilson coefficients are different from ours as is appropriate for both the b → u and the b → c transitions. In addition, we also consider the interplay of vector and scalar interactions scenarios, which are not mentioned in [13,23]. In this paper, we consider the b → u and b → c transitions together in the same framework of effective theory and perform a combined analysis using the constraints on the Wilson coefficients coming from the experimental results for the…”

Investigation of effects of new physics in Λb→ΛcτνMu1, Li2, Zou3 et al. 2019Phys. Rev. D420130View full textAdd to dashboardCite

“…If the RðD ðÃÞ Þ anomalies are due to NP, it is natural for us to ask whether its effects can be shown up in other b → cτν τ transition decays, such as B c → η c τν τ [25,26,28,89,90], B s → D ðÃÞ s τν τ [91][92][93], and Λ b → Λ c τν τ [94][95][96][97][98][99][100][101][102][103][104][105][106]. In this work, we shall study the Λ b → Λ c τν τ comprehensively in model-dependence and independence manners, as well as Λ b → Λ c lν l (l ¼ e, μ).…”